The present invention is related generally to video imaging apparatus and more particularly to apparatus utilizing plural linear arrays of charge coupled devices scanned in a "push-broom" manner past a visual field.
It is well known in the prior art to provide sensors composed of arrays of charge coupled devices for video cameras or the like. An individual charge coupled device is a small semi-conductor device which accumulates electrical charge as an approximately linear function of the incident illumination intensity and the period of exposure. In one application (e.g., a "push-broom" video imaging camera for use in an earth satellite), a multisensor video camera utilizes a plurality of sensors, each composed of a plurality of linear arrays of charge coupled devices. Each linear array sensor is nominally focused on the same underlying area through separate respective lenses responsive to "light" (including the infra and ultra visual frequencies) of a predetermined frequency range. In this manner, each linear array sensor produces an image of an elemental portion of the predetermined area composed of light of a predetermined frequency range. The images produced by the various sensors may then be superimposed to produce a composite picture or they may be used separately to obtain information related to a particular range of light frequencies.
The production of a composite picture or comparative analysis of the separate video signals is often complicated by the fact that the sensors may be mechanically and/or electrically misaligned (e.g., as a function of temperature changes, etc.) such that the actual respective elemental areas focused upon are not exactly the same. Additional problems are encountered due to the fact that each sensor may have a separate optical system (e.g., lens) in whole or in part and any variation (e.g., as a function of temperature, etc.) between these different optics will cause scale differences as well as distortion.
The present invention is for a video imaging apparatus utilizing such multiple linear arrays of sensors and having circuitry electronically compensating for mechanical and/or electrical offset between sensors and electronically compensating for scale and distortion errors caused by variations between the optical systems associated with each different array.